Cardiovascular disease is the leading cause of death in postmenopausal women in the United States. Coronary artery disease differs between men and woman in several important aspects. Lipid profiles and their associated cardiovascular risk in women differ from those in men; cigarette smoking may convey even greater risk in white women than in white men; increased risk of cardiovascular disease after menopause and the potential role of estrogen replacement therapy in reducing this risk is specific to women. Several lines of evidence support a protective role for antioxidant vitamins against oxidative damage. Several European epidemiologic studies have suggested a relationship between dietary consumption of antioxidants and coronary artery disease. This trial is a 2x2 factorial, randomized, double-masked, placebo-controlled clinical trial. The trial will randomize women to active or placebo hormone replacement therapy (conjugated equine estrogen and, when appropriate, conjugated equine estrogen with medroxyprogesterone) and to active or placebo vitamin combination (1000 mg/day of Vitamin C and 800 IU/day of Vitamin E). Patients are identified at the time of a cardiac catheterization.